Present commercial practice is to use conventional naphthenic transformer oils in transformers designed to operate under normal use at a maximum oil temperature of 90.degree. C. with an expected life in the range of about 20 to about 30 years. By operating a transformer at elevated oil temperatures of about 140.degree. C., more kilowatts of power can be generated at a higher load. Unfortunately, the conventional naphthenic transformer oils that are used in present commercial transformers have poor oxidation stability at this higher temperature and through oil oxidation become incompatible with the materials of construction of the transformer, thus significantly shortening the transformer life. Accordingly, there is a need for a transformer oil having an extended useful life at significantly higher temperatures than present oils.
One object of the invention is to provide improved electrical and transformer oils which have low solvency for materials of construction at top oil temperatures of about 140.degree. C.
Another object of the invention is to provide electrical and transformer oils that have improved oxidation stability at top oil temperatures greater than about 140.degree. C.
Another object of the invention is to provide an additive system which will impart exceptional chemical and oxidative stability to the oil and maintain the high efficiency of the transformer by not adversely affecting the power factor.
Another object of the invention is to provide electrical and transformer oils that have a negative gassing tendency.
These and other objects of the invention will become apparent upon a reading of the description which follows.